A rotary mower of the above-described general type is usually provided with a deflecting plate adjacent each of the mower assemblies. This plate is generally flat and upright, having a lower edge closely juxtaposed with the upper surface of the skirt of the mower assembly.
In order to mow the cut crop back toward the plate to form a windrow the top of the skirt is formed with radially extending ridges. As the drum rotates, the ridges orbit and pass closely beneath the lower edge of the deflecting plate, extending parallel to this lower edge at the point of closest approach of the two edges. The provision of such a ridge or ridges on the skirt aids in moving the cut crop back into a windrow, and largely prevents the crop from passing through between the deflector plate and the skirt.
The disadvantage of such an arrangement is that it often leads to blockages of the mower assembly so that the mowing operation must be halted and the operator must descend from the tractor or the like pulling the mower and clear the jam. In addition the cut crop, particularly when it is of the long-stem type, is moved with considerable violence so that it is often damaged. Furthermore the crop bunched up behind the ridge is thrown all at once against the deflecting plate so that this plate is frequently bent back after only a short time in service.